CVE-2026-42583 — netty-codec-compression
HIGHCVE-2026-42583 is a high-severity (CVSS 7.5) Uncontrolled Resource Consumption vulnerability in io.netty:netty-codec-compression. A fix is available for io.netty:netty-codec-compression — see the affected versions and patch details below.
Netty: Lz4FrameDecoder resource exhaustion
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-42583.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2026-42583 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,333 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
io.netty:netty-codec-compression☕io.netty:netty-codecReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
Description
Netty is an asynchronous, event-driven network application framework. Prior to 4.2.13.Final and 4.1.133.Final, Lz4FrameDecoder allocates a ByteBuf of size decompressedLength (up to 32 MB per block) before LZ4 runs. A peer only needs a 21-byte header plus compressedLength payload bytes - 22 bytes if compressedLength == 1 - to force that allocation. This vulnerability is fixed in 4.2.13.Final and 4.1.133.Final.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | io.netty:netty-codec-compression | all versions | 4.2.13.Finalio.netty:netty-codec-compression:4.2.13.Final |
| ☕Maven | io.netty:netty-codec | all versions | 4.1.133.Finalio.netty:netty-codec:4.1.133.Final |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for io.netty:netty-codec-compression, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update io.netty:netty-codec-compression to 4.2.13.Final or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-42583 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-42583 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-42583. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
A flaw was found in Netty's LZ4FrameDecoder. The decoder allocates a buffer based on the decompressed length from the LZ4 frame header (up to 32 MB per block) before decompression runs. A remote attacker can send a small crafted LZ4 header (as few as 22 bytes) to force excessive memory allocation, leading to a denial…
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat AMQ Broker 7.14.1 | netty-codec | RHSA-2026:66488 |
| Red Hat Data Grid 8.6.2 | netty-codec | RHSA-2026:41951 |
| Streams for Apache Kafka 2.9.4 | see advisory | RHSA-2026:34608 |
| Streams for Apache Kafka 3.2.1 | netty-codec | RHSA-2026:54435 |
| Red Hat OpenShift AI 2.25 | rhoai/odh-trustyai-service-rhel9:1788198681 | RHSA-2026:65126 |
| Red Hat OpenShift Dev Spaces 3.29 | devspaces/multicluster-redirector-rhel9:1782989027 | RHSA-2026:36820 |
Frequently Asked Questions
Is CVE-2026-42583 in your dependencies?
O3 Security finds CVE-2026-42583 across Maven dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.